To makegreen sand or like it also called molding sand (foundry sand) we need 3 ingredients: sand, clay and water.

Step 1: Digging Clay

Buy or dig some clay. I couldn’t find any clay (except fire clay) in the nearby shop and even in the big supermarket. Clay is a thing, which is not use during building, and redecoration works now. Of course, I mean that it's not used in a pure condition though it's still important ingredient in many building materials.

I had to dig some clay in the cellar. This cellar was built half a century ago, so the floor made of clay. I should also mention that this is brown clay. I’ve heard that it’s recommended to use green (bentonite clay) but I didn’t have it, so used what I had.

If clay and sand are wet, you should dry them on the sun or any other accessible way.

Step 2: Find Some Sand

Buy or dig sand. I bought sand because it was far enough to the nearest reservoir and river where it’s possible to take sand.

Step 3: Make Clay Into Fine

Make clay into fine and clean the sand if it has any contaminant.

Step 4: Formula

My formula of green sand is 70% of sand and 30 % of clay. At first, I tried to use 15% of clay but it didn’t work well. I assume, that with green bentonite clay even 15% could be fine but not brown clay.